When it comes to environmental action, no group walks the walk more than Greenpeace. At dawn today, 18 of its activists braved Arctic seas in inflatable speedboats from which they scaled an oil rig and effectively shut it down.

Greenpeace says that the Leiv Eiriksson rig, operated by Edinburgh, Scotland-based Cairn Energy, would wipe out a pristine environment in the event of an oil spill similar to BP’s 2010 blow-out in the Gulf of Mexico. A leak would not only devastate the environment but would destroy Greenland’s fishing industry, Greenpeace notes.

Activists marched to the manager’s cabin on the rig and demanded a copy of the company’s disaster recovery plan, according to a Greenpeace press release.Cairn refused to provide it.

“It’s obvious why Cairn won’t tell the world how it would clean up a BP-style oil spill here in the Arctic, and that’s because it can’t be done,” said Greenpeace mission leader Ben Ayliffe.“Experts say the freezing temperatures and remote location mean a deep water blow-out in this stunning pristine environment would be an irreversible disaster. If they published the plan, the dangers of investing in such a high-risk venture would be laid bare. We have to draw a line in the ice and stop the Arctic oil rush.”

Greenpeace noted that Cairn’s operations plans include moving icebergs out of the way by using tugs and water cannons.

Cairn released a statement saying the recovery plan is under the control of the Greenlandic administration, which is keeping it confidential. That is a normal arrangement for recovery plans, according to the statement.

“Cairn takes its responsibilities such as oil spill contingency and response plans very seriously,” the statement said. “Cairn, working closely with the Greenland authorities, has developed an extensive emergency response and oil spill response plan. As stipulated by Greenland Authorities, the oil spill response documents are not publicly available.”

After the activists climbed the rig, Cairn shut down drilling operations, citing safety reasons. By late morning, Greenland police had arrested all 18 activists and were flying them by helicopter to the capital, Nuuk.

Cairn said it plans to resume drilling from the rig, 180 kilometers (112 miles) off the Greenland coast.

Greenpeace launched the inflatable speedboats at 5 a.m. Greenland time from the Greenpeace ship Esperanza, according to the Greenpeace press release. It said the 5 boats avoided a Danish warship that has been circling the area.

Earlier in the week, Greenpeace had stopped drilling operations on the Leiv Eiriksson when two of its activists suspended themselves in pods from the rig for four days. Police apprehended them on Wednesday.

Cairn lawyers are seeking an injunction, which, according to Greenpeace, claims that it costs Cairn cost $4 million per day to shut down, and which seeks €2 million ($2.9 million) in fines for each day the group subsequently shuts down operations.

Cairn said it has filed for the injunction in Holland, to prevent “future disruption of Cairn’s lawful operations offshore Greenland.”

Larger oil companies including Exxon Mobil and Chevron have also bought licenses to drill off Greenland as the industry gears up for a possible Arctic boom.